Transplantation is an exciting and rapidly expanding field with great potential for curing human disease. The purpose of this institutional training program is to provide opportunities for young scientists and physician scientists for training in a wide variety of topics related to basic research transplantation immunology with an emphasis on immunological mechanisms. To this end, we have developed a Harvard Longwood Medical Area wide combined training program in which a highly collaborative and productive group of faculty with diverse but complementary research interests, a record of collaboration, and a commitment to training young investigators will serve to mentor individuals committed to a career in transplantation biology. The faculty will provide pre- and postdoctoral trainees with the opportunity to receive training in topics related to transplantation immunology including tolerance, T cell activation, MHC structure and function, gene therapy, lymphocyte trafficking, bone marrow transplantation, vascular biology, stem cell biology, regulation of lymphocyte development, infectious disease, autoimmunity, islet transplantation, bioinformatics, and xenotransplantation. The major goal is to produce outstanding independent investigators capable of addressing fundamental questions in the field of transplantation. The experience and dedication of the faculty, as well as the research environment comprised of the major teaching hospital within the Harvard Longwood Medical Area and Harvard Medical School provide a unique environment in which this goal can be accomplished. Pre-doctoral trainees will be selected from the Immunology Program at Harvard University's Division of Medical Sciences based on their interest in pursuing dissertation research in the field of transplantation immunology. Support is requested for 1 pre-doctoral trainee in year 1 and 2 in all subsequent years, distributed between students in their 1st, 2nd 3rd, or 4th year of thesis research. Training for pre-doctoral students will take approximately 4 years. Postdoctoral trainees currently holding a degree of MD, PhD, or MD, PhD will be selected based on having outstanding potential to pursue a career in research and teaching and a commitment to independent investigation. Support is requested for 2 postdoctoral trainees in year 1 and 4 in years 2 through 5 of the training proposal. Training will require 3 years. Trainees will choose a primary research advisor from the participating training faculty that will oversee daily research endeavors of the trainee. All trainees will participate in an interactive environment comprised of formal course work, departmental and interdepartmental seminar series, journal club, and laboratory meetings. This interactive environment will insure that all trainees are exposed to a wide variety of disciplines and will help prepare them for an independent career in transplantation immunology, a field with direct relevance to human health.